ADSORPTION AND DISSOCIATION OF DIMETHYL ETHER ON CLEAN AND OXYGEN-DOSED RH(111)

The interaction of dimethyl ether (DME) with clean and oxygen-covered Rh(111) surfaces has been investigated by TDS and HREELS. The adsorpti on of DME on the clean Rh(111) surface was reversible at 100 K; all th e adsorbed DME was released to the gas phase after annealing without a ny sign of decomposition. On increasing the adsorption temperature to 250-300 K, the appearance of an intense HREELS feature at 1230 cm(-1) indicated that a reaction channel opened up for the thermally activate d decomposition of DME. The reaction intermediate of this process was tentatively identified as CHO or CHxOCHx(a) species, the decomposition of which resulted in adsorbed CO and hydrogen. On the O-precovered Rh (111) surface, a fraction of DME was stabilised in a state characteriz ed by T-p = 245 K. On the other hand, the interaction of DME with adso rbed O led to the formation of CH3O(a) species at 100-195 K. Above 250 K, this species is decomposed and oxidized, leading to the evolution of H2O and CO2. (C) 1997 Elsevier Science B.V.